The role of echocardiography in the evaluation of mechanical complications of acute myocardial infarction.

With the introduction of the coronary care unit and more effective therapy for primary life-threatening arrhythmias, cardiogenic shock and the mechanical complications of acute myocardial infarction are now responsible for the majority of in-hospital deaths. These mechanical complications, which include myocardial rupture of the left ventricular free wall, rupture of the ventricular septum, and rupture of the papillary muscle, are estimated to account for 25,000 fatalities yearly in the United States. Although the mechanism of myocardial rupture has not been clearly defined, there is increasing evidence that infarct expansion, which can be readily detected by two-dimensional echocardiography, may be an important pathophysiologic factor. The ready availability of echocardiography in the coronary care unit has made a major impact on the immediate diagnosis of mechanical complications in the hemodynamically compromised patient with acute myocardial infarction. In particular, two-dimensional and Doppler echocardiographic techniques have been extremely useful in the identification and localization of ventricular septal rupture. In addition, papillary muscle rupture can be readily diagnosed by Doppler approaches and is easily distinguished from ventricular septal rupture. In view of increasing evidence that early surgical intervention is indicated in these patients, these echocardiographic approaches offer the surgeon prompt diagnostic and anatomic information. Unfortunately, rupture of the free wall of the left ventricle often results in sudden death within minutes before echocardiographic evaluation can be attempted. Nevertheless, rapid echocardiographic diagnosis provides the patient with the possibility of potential life-saving resuscitative interventions before immediate surgery. Thus, over the past decade, echocardiography has become a vital tool in the diagnosis and evaluation of patients with mechanical complications of acute myocardial infarction. The development of Doppler techniques, color flow Doppler, and esophageal approaches should further enhance our diagnostic abilities and allow careful monitoring of patients before, during, and after surgical repair. It is hoped that with the improvements in echocardiographic evaluation of mechanical rupture and more rapid surgical intervention, future studies will demonstrate better surgical results with good long-term survival in patients with myocardial rupture.